* Add support for running UAT with an absolute path to the editor executable, and pass a full path when cooking or packaging.
* Fix path to the editor executable when launching a standalone editor instance for preview.
#jira UE-70785
#rb none
#ROBOMERGE-OWNER: ben.marsh
#ROBOMERGE-AUTHOR: ben.marsh
#ROBOMERGE-SOURCE: CL 5238647 in //UE4/Release-4.22/... via CL 5238651
#ROBOMERGE-BOT: BUILD (Main -> Dev-Build)
[CL 5250912 by ben marsh in Dev-Build branch]
12ba6c3a8f